1. Literally, a situation that may cause discomfort to both the bonee, and other parties involved, in a formal setting (i.e. a dinner party).
2. Used as an expression, it signifies something or someone unwanted or out of place, something in an unsuitable setting.
1. Nobody appreciated when Alan got a boner at Alice's dinner party.
2. When Doug arrived at his niece's 3rd birthday party wearing assless chaps, all the guests agreed he was a boner at a dinner party.
Someone farts in a social setting. This can be heard, smelled, or both. A fine way to draw red cheeks from the offending guest is to casually mention that someone has had dinner with Connie. Connie is a name associated with a person unwilling ever to admit that she ever farts.
A telltale noise goes off between someone's legs at a social gathering. "Well, it seems as someone's had dinner with Connie."